Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption

• DOI: 10.1016/j.heliyon.2023.e21735
• Publication Date: 2023-11-01T01:04:58Z
• Authors: Amarjeet Dahiya; Akanksha Bhardwaj; Archana Rani; Meenu Arora; J. Nagendra Babu
• Keywords: Hexavalent Chromium; Langmuir adsorption model

Surface oxygen functional groups of biochar were tuned by oxidation and reduction for establishing Cr(VI) adsorption mechanism. Oxygen (OFGs) on the surface leached rice straw (LBC4-6) obtained from pyrolysis at 400, 500 600 °C, oxidized to furnish OBC4-6 using modified Hummer's method. Reduced RBC4-6 esterification NaBH4/I2 (OBC4-6). The characterized increase in O/C H/C ratio, respectively, case RBC4-6. LBC4-6, OBC4-6, showed optimum conditions pH 3 dose 0.1 g/L with a good non-linear fit Langmuir & Freundlich isotherm. maximum (Qm) followed trend: OBC4 (17.47 mg/g) > RBC4 (15.23) OBC5 (13.23) LBC4 (10.23) RBC5 (9.83) OBC6 (9.60) RBC6 (7.24) LBC5 (6.32) LBC6 (5.98). kinetics fits pseudo second order (PSO), Elovich intraparticle diffusion kinetics, showing chemisorptions L/O/RBC4-6. lower temperature O/RBC4 show better adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish OFGs chelation reduced Cr(III). Adsorption stripping cycles as adsorbents excellent Cr up >98 % upon desorption 1 M NaOH.